This invention relates to a production method for an absorbent article (body) used for pet sheets, disposable diapers, sanitary napkins, and the like.
Conventional production methods for producing absorbent bodies are explained with reference to FIGS. 13 and 14.
In the conventional production method of an absorbent body shown in FIG. 13, a carrier tissue 2 is drawn from a roll 2a which is supported by an axis 1 and is forwarded continuously. A pulp supplier 3 is provided above the carrier tissue 2 which is forwarded continuously. Crushed pulps are supplied from the pulp supplier 3 to be poured on the carrier tissue 2. A supply nozzle 4 for supplying particulate SAP (super-absorbent polymers) is provided above the carrier tissue 2, and supplies the SAP on the carrier tissue 2 which is forwarded continuously.
A suction chamber 6 is provided opposite the pulp supplier 3 and the supply nozzle 4 with the carrier tissue 2 interposed. Crushed pulp and the SAP are sucked by the suction chamber 6 to form a strip of an absorbent material layer 5 comprised of a mixture of crushed pulp and SAP on the carrier tissue 2.
For a faster production, crushed pulp and SAP are continuously supplied onto the carrier tissue 2 to form a strip of an absorbent material layer 5. Thereafter, a cover tissue (not shown) is supplied onto the strip of the absorbent material layer 5 to form a laminated body, which comprises the carrier tissue 2, a cover tissue and the absorbent material layer 5 interposed between the tissues. Both sides of the laminated body are then cut by a cutter, such as a rotary cutter, and thereafter the laminated body is cut into individual absorbent bodies.
In the conventional production method of an absorbent body shown in FIG. 14, the carrier tissue 2 drawn from the roll 2a is forwarded continuously. A circular pattern drum 7 is provided above the carrier tissue 2 which is forwarded continuously. The pattern drum 7 rotates in the clockwise direction around the axis 8 at the running speed of the carrier tissue 2.
Concavities 9 are provided on the outer face of the pattern drum 7 at predetermined intervals. Mesh 9a of a predetermined screen dimension is provided at the bottom of the concavity 9. The concavity 9 is formed in a predetermined shape such as the shape of an hourglass. A pulp supplier 11 is provided above the pattern drum 7, facing the outer surface of the pattern drum 7. A supply nozzle 12 for supplying SAP is provided also facing the outer surface of the pattern drum 7.
According to the production method of the absorbent body as shown in FIG. 14, crushed pulp is supplied from the pulp supplier 11 into the concavity 9 which is provided on the outer surface of the rotating pattern drum 7. Also, SAP is supplied from the nozzle 12 into the concavity 9 in the same manner.
A suction means is provided inside of the pattern drum 7 facing the pulp supplier 11 and the supply nozzle 12 for sucking air through the openings of the mesh 9a provided at the bottom of the concavity 9. The crushed pulps and the particulate SAP are sucked onto the concavity 9, thereby forming an absorbent material layer 13 having the same shape as the concavity 9.
At the time the concavity 9 faces the carrier tissue 2 during the course of rotation of the pattern drum 7, another suction means provided below the carrier tissue 2 sucks air through the carrier tissue 2. By this suction, the absorbent material layer 13 is transferred onto the carrier tissue 2. Subsequently, a cover tissue (not shown) is laid along the carrier tissue 2 and the absorbent material layer 13, thereby forming a laminated body comprised of the carrier tissue 2, the cover tissue and the absorbent material layer 13 interposed between the tissues. Thereafter, the carrier tissue 2 and the cover tissue are cut in accordance with the shape of the absorbent material layer 13 to produce individual absorbent bodies.
In high speed production of the absorbent body, according to the conventional production method shown in FIG. 13, because the absorbent material layer 5 is formed in a strip shape on the carrier tissue 2 in a continuous process, a rectangular absorbent body is produced. However, it is almost impossible to produce an absorbent body having a desired shape, such as an hour glass shape. Therefore, in order to produce an absorbent body having a desired shape, e.g., hour glass shape, it is necessary to perform a trimming process to such laminated body in a press working process. However, this results in many additional processing steps.
In addition, in order to laminate another absorbent material layer on the absorbent material layer 5 formed by the conventional production method shown in FIG. 13, crushed pulp and SAP must be sucked by the suction means through the carrier tissue 2 and the absorbent material layer 5. However, due to the poor air permeability of the laminated layers formed from the carrier tissue 2 and the absorbent material 5, it is almost impossible to form another absorbent material layer over the laminated body by sucking additional crushed pulp or SAP by the suction means. For this reason, in the production of the absorbent body having two absorbent material layers laminated, each of the absorbent material layers must be produced separately by the method shown in FIG. 13 and each laminated thereafter. Therefore, conventional methods inevitably use many production steps to produce an absorbent body having two absorbent material layers therein.
Moreover, in order to cut an absorbent body having two laminated absorbent material layers therein, another cover tissue must to be laid over the absorbent material layer at the upper side. Consequently, at least three tissue layers are needed, making the production of the absorbent body expensive.
On the other hand, according to the conventional production method of the absorbent body shown in FIG. 14, the absorbent material layer 13 can be formed in the same shape as that of the concavity 9 formed on the outer face of the pattern drum 7.
However, in order to form the absorbent material layer 13 in the same shape as that of the concavity 9, crushed pulp and particulate SAP must be sucked into the concavity 9 by the suction force through the openings of the mesh 9a provided at the bottom of the concavity 9. In general, the opening size of the mesh 9a is 60 mesh (according to the standard of Tyler, U.S.A. the opening size of such mesh is equal to 0.246 mm).
However, because of the fineness of the SAP supplied to the concavity 9, SAP easily passes into the inside of the pattern drum 7 through the mesh 9a, thereby rendering a very poor yield ratio of SAP. Due to the passage of SAP through the mesh 9a, which results in a poor yield ratio of SAP, it is very difficult to increase the content of SAP in the absorbent layer 13. Therefore, it is extremely difficult to produce an absorbent layer containing 20% SAP or more by weight.
Further, in order to accelerate the liquid absorption speed of the absorbent material layer, the particle size of SAP present in the absorbent material layer must be very small. However, the mesh 9a having the opening size of 60 mesh can hardly prevent such fine SAP from passing through into the pattern drum 7. Therefore, it is almost impossible for the mesh 9a to hold SAP having a small particle size, such as 100 mesh or less (which passes through a mesh having an opening size of 0.147 mm) at the concavity 9.
In addition, according to the conventional production method shown in FIG. 14, the absorbent material layer 13 must be sucked through the carrier tissue 2 by the suction means provided below the carrier tissue 2 at the time the concavity 9 faces the carrier tissue 2. However, in order to suck the absorbent material layer formed in the concavity 9 through the carrier tissue 2, a very strong suction force is needed. Consequently, the suction means inevitably becomes large, making the production cost very high.
Furthermore, according to the conventional production method as shown in FIG. 14, it is very difficult to produce an absorbent body having two absorbent material layers laminated to each other. Sucking another absorbent material layer onto the absorbent body, by sucking through the carrier tissue 2 and the absorbent material layer 13 using a suction means, is almost impossible because of the poor air permeability of the layers. Therefore, in order to produce an absorbent body having two absorbent material layers laminated therein, each of the absorbent material layers must be produced separately and thereafter laminated to each other, such as the production method shown in FIG. 13. Consequently, the number of steps for producing the absorbent body having two absorbent material layers laminated to each other is inevitably increased.
Also, similar to the production method shown in FIG. 13, in order to cut the absorbent body having two laminated absorbent material layers therein, another cover tissue must be laid over the absorbent material layer at the upper side. As a result, at least three tissue layers become necessary, making the production of the absorbent body expensive.
It is an object of the present invention to provide a production method of an absorbent body which overcomes the aforementioned problems by transferring the absorbent material layer formed in the concavity of the pattern drum onto the cover sheet without using a large scaled suction means of the conventional technology.
It is a further object of the present invention to improve the yield ratio of SAP present in the absorbent material layer, thereby achieving an absorbent body containing an increased amount of SAP or fine SAP.
It is a further object of the present invention to provide a production method of an absorbent body that can laminate a plurality of absorbent material layers without using a cover sheet between the laminated absorbent material layers.
It is a further object of the present invention to produce an absorbent body by laminating a plurality of absorbent material layers wherein each layer can have a different shape, different SAP contents, or different particle sizes for SAP.
To achieve these objects, the production method of the present invention comprises the steps of:
(1) supplying a first cover sheet on an outer surface of a rotating pattern drum, said pattern drum provided with a concavity formed in a predetermined shape on the outer surface thereof;
(2) adapting the first cover sheet to the shape of the concavity and supplying an absorbent material into the concavity to form an absorbent material layer adapted to the shape of the concavity on the first cover sheet;
(3) supplying a second cover sheet toward the outer surface of the pattern drum; and
(4) separating the first cover sheet together with the absorbent material layer from the outer surface of the pattern drum and superposing the first cover sheet together with the absorbent material layer on the second cover sheet to produce an absorbent body comprised of the first cover sheet, the second cover sheet and the absorbent material layer interposed between the first cover sheet and the second cover sheet.
In this production method, it is also possible that another absorbent material layer is formed on the second cover sheet, and the absorbent material layer formed on the first cover sheet is superposed on the absorbent material layer formed on the second cover sheet, between the first cover sheet and the second cover sheet.
Another production method of the absorbent body according to the present invention comprises the steps of:
(1) supplying a first cover sheet on an outer surface of a first pattern drum rotating, said first pattern drum being provided with a first concavity formed in a predetermined shape on the outer surface thereof;
(2) adapting the first cover sheet to the shape of the first concavity and supplying an absorbent material into the first concavity to form a first absorbent material layer adapted to the shape of the first concavity on the first cover sheet;
(3) supplying a second cover sheet on the outer surface of a second pattern drum rotating, said second pattern drum being provided with a second concavity formed in a predetermined shape on the outer surface thereof;
(4) adapting the second cover sheet to the shape of the second concavity and supplying an absorbent material into the second concavity to form a second absorbent material layer adapted to the shape of the second concavity on the second cover sheet; and
(5) separating the first cover sheet together with the first absorbent material layer from the outer surface of the first pattern drum and separating the second cover sheet together with the second absorbent material layer from the outer surface of the second pattern drum and superposing the first cover sheet together with the first absorbent material layer on the second cover sheet together with the second absorbent material layer to produce an absorbent body comprised of the first cover sheet, the second cover sheet and the first and second absorbent material layers interposed between the first cover sheet and the second cover sheet.